Enhance imagery source selector card

[vgeorge]

We should consider replacing the timestamps in imagery source cards with some other context, like a short text describing the source. The timestamps refer to database insert/update and don't look to be of interest to end users. (as suggested in #56 (comment))

cc @geohacker @LanesGood

[LanesGood]

I agree with this. Does all the imagery source info come from Planetary Computer? They provide a thumbnail and text description for each source. I think we can pull in both:

[geohacker]

Would be great to do! We can assume that PEARL will always rely on imagery from Planetary Computer

[vgeorge]

Just an update, the cards currently display the start/end timestamp of the mosaic range, not the record creation/update time.

[vgeorge]

Apologies, I thought this was referring to the mosaic selector, not to the imagery source. I confirm the interface is displaying the database timestamps for imagery sources.